#define _CRT_SECURE_NO_WARNINGS
#include"stdio.h"
int main() {
	double sum = 0.0;
	int change = 1;
	for (int i = 1; i <= 100; i++) {
		sum += change*1.0 / i;
		change = -change;
	}
	printf("%lf\n", sum);
	return 0;
}